On 6/19/2026 8:31 AM, Ackerley Tng via B4 Relay wrote:
From: Ackerley Tng <[email protected]>
Introduce function for KVM to check the private/shared status of guest
memory at a given GFN.
This will be used in a later patch.
Signed-off-by: Ackerley Tng <[email protected]>
Co-developed-by: Sean Christopherson <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
With binbin's comment resolved,
Reviewed-by: Xiaoyao Li <[email protected]>
BTW, it looks better to move the patch 01 just behind this one.
---
include/linux/kvm_host.h | 2 ++
virt/kvm/guest_memfd.c | 31 +++++++++++++++++++++++++++++++
2 files changed, 33 insertions(+)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3915da2a61778..27687fb9d5201 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2575,6 +2575,8 @@ static inline bool kvm_mem_is_private(struct kvm *kvm,
gfn_t gfn)
#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
#ifdef CONFIG_KVM_GUEST_MEMFD
+bool kvm_gmem_is_private(struct kvm *kvm, gfn_t gfn);
+
int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
int *max_order);
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 8101f64e0366f..bca912db5be6e 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -510,6 +510,37 @@ static int kvm_gmem_mmap(struct file *file, struct
vm_area_struct *vma)
return 0;
}
+bool kvm_gmem_is_private(struct kvm *kvm, gfn_t gfn)
+{
+ struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
+ struct inode *inode;
+
+ /*
+ * If this gfn has no associated memslot, there's no chance of the gfn
+ * being backed by private memory, since guest_memfd must be used for
+ * private memory, and guest_memfd must be associated with some memslot.
+ */
+ if (!slot)
+ return 0;
+
+ CLASS(gmem_get_file, file)(slot);
+ if (!file)
+ return 0;
+
+ inode = file_inode(file);
+
+ /*
+ * Rely on the maple tree's internal RCU lock to ensure a
+ * stable result. This result can become stale as soon as the
+ * lock is dropped, so the caller _must_ still protect
+ * consumption of private vs. shared by checking
+ * mmu_invalidate_retry_gfn() under mmu_lock to serialize
+ * against ongoing attribute updates.
+ */
+ return kvm_gmem_is_private_mem(inode, kvm_gmem_get_index(slot, gfn));
+}
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_is_private);
+
static struct file_operations kvm_gmem_fops = {
.mmap = kvm_gmem_mmap,
.open = generic_file_open,
